The intraluminal delivery of diagnostic catheters, treatment fluids, expansion devices or stents is commonly used to diagnose or treat defects, such as blockages and stenoses, within the human vasculature. Expansion devices can take a number of forms, including a balloon that is inflated to open the blockage. The use of a balloon may provide only a temporary solution and a stent may be inserted after or instead of the balloon as a more permanent solution.
When treating defects in peripheral, coronary or neural blood vessels, it is usually necessary to pass the treatment or diagnostic device through tortuous paths in the vasculature, and often through narrow constrictions, to reach the desired site. To accomplish this, the devices often are delivered by a catheter. Catheters generally have a tubular shaft with a lumen and may include an inner member. To guide the catheter through the vasculature to the desired site, catheters can be passed over a guidewire.
The parameters of trackability, pushability and crossability are often assessed when discussing catheter performance. An optimal design would allow the catheter to easily follow the path of the vasculature (trackability) and to readily traverse narrow constrictions in the vasculature (crossability) but would not substantially affect the ability to transmit force from the proximal end to the distal end of the catheter (pushability).
Trackability and crossability are improved by the properties of the most distal portion of the catheter: A flexible distal portion improves performance of the catheter with respect to these parameters. However, the catheter body must not be too flexible or pushability will be adversely affected. To attempt to reconcile these differing requirements, catheters have been designed that have a flexible distal portion but a stiffer proximal portion. However, these catheters often require elaborate designs that are difficult to manufacture. For example, Griffin et al., U.S. Pat. No. 7,001,369 describes a device that requires multiple reinforcement layers and the use of several types of materials to achieve the required properties. Other devices having catheter shaft variations are found in Jordan et al. U.S. Patent Application Publication No. 2005/0288628 and Sherman et al. U.S. Patent Application Publication No. 2006/0030835. Each patent or publication referred to is herein incorporated by reference.
A need remains for an effective but simple-to-use and easily manufactured catheter structure that allows for flexibility while maintaining adequate stiffness in important areas of the inner tubular body of the catheter. At times it is desired to have a catheter inner tubular body that allows for flexibility or stiffness in selected areas.